Re: [PATCH] block: blk-zoned: fix zwplug refcount leak on write error path

[Haris Iqbal <haris.iqbal@linux.dev>]

On 5/26/26 16:18, Wentao Liang wrote:
> blk_zone_wplug_handle_write() increments zwplug->ref via kref_get()
> when preparing to handle a zone write. On the error path where
> blk_zone_wplug_handle_write_noalloc() fails, the function returns
> without calling kref_put() on zwplug->ref, leaking the reference.
> 
> Add kref_put(&zwplug->ref, ...) on the error path to properly release
> the reference.
> 
> Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
> ---
>   block/blk-zoned.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 42ef830054dc..24b899663a48 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -1503,6 +1503,7 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
>   
>   	if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
>   		spin_unlock_irqrestore(&zwplug->lock, flags);
> +		disk_put_zone_wplug(zwplug);

I am not sure if this is needed. The code above adds the 
BIO_ZONE_WRITE_PLUGGING flag to the bio, which means the 
blk_zone_write_plug_bio_endio would be called which should then call 
disk_put_zone_wplug.

I do wonder if there are special cases when blk_zone_bio_endio is not 
called.

>   		bio_io_error(bio);
>   		return true;
>   	}
> @@ -1511,6 +1512,7 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
>   	zwplug->flags |= BLK_ZONE_WPLUG_PLUGGED;
>   
>   	spin_unlock_irqrestore(&zwplug->lock, flags);
> +	disk_put_zone_wplug(zwplug);
>   
>   	return false;
>